package week10;

public class Main6_3 {
	public static void main(String[] args) {
		
	}
}

class A
{
	public Integer push(Integer item);
	{
		if(item == null)
			return null;
		if(top==arrStack.length)
			throw new FullStackException();
		arrStack[top++]=item;
		return item;
	}
	public Integer pop();
	{
		if(top==0)
			throw new EmptyStackException();
		return arrStack[--top];
	}
	public Integer peek();
	{
		if(top==0)
			throw new EmptyStackException();
		return arrStack[top-1];
	}
}